What did he mean?!

Serenity stared blankly at Jackson only to see his almost perfectly exquisite lips part, and the next words that came out of his mouth were, "Haven't you always longed for a family, Sis? Then why don't you keep on being my Sis?"

Serenity was shocked into silence. After a while, she suddenly got an urge to burst out into a roar of laughter.

"You want me to continue being your sister and you'll be my younger brother?"

"Why not?" he asked her.

"Don't you realize how comical